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R S CHLIN ATT ION MILL Filed July 5, 192'? Aug. 6, 929.

Patented Aug. 6, 1929.

UNITED STATES PATENT OFFICE.

ROBERT S. MECHLEN, OF SPRINGFIELD, OHIO, ASSIGNOR TO THE BAUER BROTHERSCOMPANY, OF SPRINGFIELD, OHIO, A CORPORATION OF OHIO.

ATTRITION MILL.

This invention relates to grinding plates for attrition mills, itparticularly relating to that type ot plate which has ribs extending onradial. lines and other ribs extending on chordal lines.

The object of the invention is to so arrange the ribs as to avoidsinnilta-neous registration at any one time of the major portion of theribs of opposed grinding plates to thereby reduce friction betweenopposing 'ilates and enable a larger quantity of material to be groundto a liner degree with thesame amount of power, or less: also todistribute the wear upon the plates in a more uniform manner and providefor a more etl cctive grlnding areajand also to allow for a free flow ofma terial between the plates.

To that end, the invention consists in arranging the grinding surfacesinto sectors, with each sectorprovided with a. plurality ot series ofparallel ribs which extend along chordal lines and a plurality of seriesof ribs which extend along radial lines, with the chordal ribs of oneseries in staggered rela tion with those of another series, and witheach series of radial ribs so disposed in relation to the other seriesthat these radial ribs will be in more or less staggered relation to theribs of an opposing sector at all times and especially when opposingsectors are in completc registry.

A "further object of the invention is to provide an outercircumferential rib of zig-zag or saw-tooth form to reduce the frictionadjacent the outer periphery of the grinding plates, and. to also imparta final reduction to the material.

In the accompanying drawings:

Fig. 1 is an elevation of the working face of a portion of a grindinghead equippedwith my improved. plates.

Fig. 2 is an elevation of the working face of one of the plates showingin dotted lines an opposing plate in registry therewith to disclose therelation oi the ribs when oppos ing plates are in registry.

Referring to the drawings. 1 represents a portion of the grinding headof an attrition mill. For manufacturing reasons, the grinding surfacesof these heads are in the form of a series of platessecured to theheads. One of these plates is shown complete at 2, and

3 and 4; represent portions of other adjacent plates. The ribs are sodisposed on the plates that when the plates are all assembled on a headthe grinding surface is divided into a series of sectors in which thechordal ribs of each sector are in parallel planes. For instance,referring to Fig. 1 of the drawings, there are shown three completesectors indicated at a, b and c and portions-of two other sectors (Z and6. Each individual plate contains one complete sector and portions oftwo other sectors, as shown in Fig. 2 in which the sector 6 is showncomplete while one-half only of each of the sectors a and c aredisclosed, adjacent plates forming the other half of each of thesesectors a and 0. Each sector is provided with two series of ribs 5 and 6arranged in parallel planes butxwith the ribs 5 of one series instaggered relation to the ribs 6 of the other series. Each of these ribs5 and 6 extends on a line which forms a chord of a circle whose centeris the center of the Each sector also has a plurality of rows ofradially extending ribs arranged different distances from the centerandextending between the ehordal ribs, those rows on one side of thesector being indicated at 7 and those on the opposite side at 8. Theribs ofeach row are arranged varying distances apart. For instance, theribs 7 of the first lower-most row in the present case are so separatedthat the pockets between them decrease in width progressively in aclock-wise direction while the ribs 8 of the lower-most row aresimilarly arranged. In the neXt'row above, the width of the pocketsformed by ribs 7 increase progressively in a clock-wise direction as doalso the width of the pockets formed by ribs 8. In the next rowoutwardly, the pockets formed by the major portion of the ribs 7decrease in a clock-wise direction as do the pockets formed by the magor portion of the ribs 8. In the latter row, however, this rule does nothold good as to the two outer pockets in each row, but the widthsofthese pockets nevertheless vary. The two outer-most rows of ribs 7 and 8are likewise disposed at varying distances apart. By this arrangement,the majority of the radial ribs of opposing sectors will at all times bemore or less in staggered relation and this will be particularly truewhen two opposing sectors are in complete registry as shown in Fig. 2.

Each plate also has an outer circumferentially extending rib 9 which isof a zig-zag or saw tooth form as shown.

The result of this construction is illustrated in Fig. 2 in which itwillbe seen that when two opposing plates are in exact registry the chordalribs 5 and 6 of opposing sectors will occupy the position shown in fulland dotted lines, with no two opposed ribs in registry with each other.The same thing is substantially true of the radial ribs as it will beseen that-the major portion of these ribs are completely out ofregistryor only partly in regisfaces leading to the periphery of the heads andthe material is fed to the heads through a central eye in one of theheads and is thrown outwardly by centrifugal force, the material passingfrom pocket to pocket formed by the This arrangement of ribs,therefore, not only reduces the friction caused by the .materialbetweenopposing ribs, but also allows for a more uniform flow of the materialoutwardly to the periphery of the-heads be- I cause of the fact that iteliminates the periodic cessation of flow which exists in those grindingheads in-which there is a periodic complete registry of all the ribs ofopposed grind- .ing surfaces, which has the effect, it will beunderstood, of checking the flow of material when such complete registrytakes place.

I 7 It will be understood that in the operation ,ofgrinding headsof thischaracter, one or both of the heads revolve and the chordal A0 andradial ribs of opposing heads co-act with a shearing action to reducethe material.

Having thus described my invention, I claim:

1. In an attrition mill, a grinding head having a grinding surfaceprovided with ribs positioned to divide the surface into sectors, aplurality of series of parallel chordally eX- tending ribs on eachsector, with the ribs of one series in staggered relation with the ribsof an adjacent series, and av plurality of series of substantiallyradially extending ribs on each sector so disposed that the radial ribsof one series will be in staggered relation with the ribs of an opposingsimilarly formed sector when said opposing sectors are in registry.

2. An attrition mill, a grinding head having a grinding surface providedwith ribs positioned to divide the surface into sectors including aplurality of series of substantially radially extending ribs on eachsector so disosed that the radial ribs of one series will Be instaggered relation with the radial ribs of an opposing similarly formedsector when said opposing sectors are in registry.

3. An ,attration mill, a grinding head having a plurality of segmentalplates, saidplatcs being .of uniform construction and provided with ribspositionedto divide the surface of the head into sectors, ear-h sectorhaving two series of parallel chord-ally eztending ribs with the ribs ofone series in staggered relation with the adjacent series, each. sectoralso having two-series of substantially radially 0:;-

In testimony whereof, I have hereunto set my hand this 1st day of July,1927.

ROBERT S. MECl-ILIN.

